Methicillin-resistant Staphylococcus aureus (MRSA) are Staphylococcus aureus strains characterized by their resistance to an antibiotic, methicillin, and to related antibiotics such as oxacillin. MRSA bacteria represent a high percentage of nosocomial infections, and are often responsible for serious and potentially fatal health problems. Most commonly cross-transmitted between patients via the healthcare staff, MRSA are responsible for endemic infections that are very difficult to control. In addition to an appropriate treatment, the screening for MRSA carriers and the isolation of colonized patients constitute the most effective methods recommended today by official organizations such as the Society for Healthcare Epidemiology of America. Early and systematic screening is therefore essential.
MRSA can be detected by various techniques.
It is possible to detect MRSA by molecular biology techniques. In this respect, mention may in particular be made of Application EP887424. However, such methods remain expensive as a routine test, and require qualified staff.
It is also possible to use conventional culture media for detecting Staphylococcus aureus, such as the medium described in Application EP 1390524. The detection of MRSA is carried out in an additional step, by means of a specific agglutination test (Slidex MRSA, bioMérieux) or by means of an agar diffusion method in the presence of an oxacillin, cefoxitin or latamoxef disc (recommendations of the Comité de l'Antibiogramme de la Société Française de Microbiologic (Antibiogram Committee of the French Society for Microbiology) and of the Clinical Laboratory Standard Institute).
It is also possible to culture bacteria that may be MRSA on agar media in the presence of antibiotics. Such media may also be chromogenic, thereby facilitating the reading and detection of the MRSA. Mention may in particular be made of the medium described in Application EP 1543147. However, because the detection of a phosphatase activity under the conditions described is not very specific, it is necessary to combine it with the detection of several other enzymatic activities, thereby reducing the fertility of the medium and increasing the cost thereof.